Standardized and reusable software (SW) objects (or SW components - in-house or pre-fabricated) are increasingly being used to reduce the cost of software (SW) development. Given that the basic components may not have been developed with dependability as primary driver, these components need to be adapted to deal with errors from their environment. To achieve this, error containment wrappers are added to increase the reliability of the components. In this paper, we first present a modular specification approach using fault intolerant components, based on the concepts of category theory. We further introduce the concept of wrapper consistency, based upon which, we present an algorithm that systematically generates globally consistent fault containment wrappers for each component, to make them fault tolerant. Subsequently, we enhance the initial modular specification to deal with the wrapped components, and show that safety properties of the system are preserved under composition only if the wrappers are globally consistent.